Conventionally, there is a power supply control device including a plurality of switching elements connected parallel to each other between a battery and a load, and is configured to detect a failure of any one of the switching elements (see JP-A-2011-229216). Specifically, the power supply control device measures voltages at terminals of the switching elements on the load side while the switching elements are individually opened and while the switching elements are opened at the same time (open state). Then, the power supply control device detects a failure of each switching element based on the measured voltages. Such a failure of the switching element includes a close failure in which the switching element remains closed (close state) even when an open instruction signal for opening the switching element is input.
According to the above conventional technology, all switching elements need to be opened at the same time to determine whether failures of switches exist. Therefore, a current path between the battery and the load is shut off.
This specification describes a technology for determining whether a failure of switch exists without shutting off a current path between an electric storage device and an electric device such as a load and a charger.